Summary Edexcel IAS Level Biology Unit 2 Complete Notes

, Topic 3 : CELL STRUCTURE , REPRODUCTION AND DEVELOPMENT

3A : CELL STRUCTURE

Observing cells


Cells
·
are biological functional Units
of organisms
used because
Microscopes are to observe cells of their small size
-




There two
types of
:
are
microscopes
-




>
Light Coptical)
> Electron




I
Light Electron

Electron beams used to
Light is used to illuminate are
· ·




the illuminate the
sample sample
·
Low resolution (wavelength of light) ⑧


High resolution (wavelength of electrons)

Used live May kill the live
for samples sample
· ·




Cheaper Expensive
· ·




false
Portable light images Not
+
portable
· ·




If due to
staining
May produce artefacts
[
·




staining
·
staining is used to see the inside of thecell


Different stains used
for different types of sample
-


are


>
haematoxylin-stains the nuclei


blue brown
-purple , or



>
methylene blue-stains animal nuclei

-
blue
> acetocarmine -
stains chromosomes



>
iocline starch
stains
containing material
-




-

blue black

Magnification
magnification= Image size
total objective (ens lens
magnification X
eye piece
:




Actual size


Image Size :
Actual Size -
magnification um-mierometre

Actual size :
Image Size -
X10-5


magnification

, Eukaryotic Cells


Eukaryotic cells are
complex
-




They have a membrane-bound nucleus

Structures

① Membrane ⑧ Rough endoplasmic reticulum (RER)

Localises -involved production and
enzymes reaction
pathways in
-

in



transport of proteins
②
Protoplasm
The ⑨ Smooth
cytoplasm and nucleus combined
endoplasmic reticulum
-




-involved the and
in
synthesis
③ Nucleus
transport of steroids and

contains DNA RNA and
protein lipids
-




,

-

surrounded by a double nuclear membrane


with
pores 10 Golgi apparatus
-

stacks extracellular made

& Mitochondria membranes and
packages
site for them transport
anaerobic
respiration for
-




releases ATP molecules
-




⑪ Centrosomes

③ Centrioles -




organises the microtubles and


-
involved in cell division provides structure to the cell




⑥ Ribosomes

20s

-consists ribosomal RNA
of
-
made
of 60s and 40s
up
Site
for protein Synthesis
-




70s
-




-

found in Mitochondria




① Lysosomes
contain digestive enzymes apoptosis
-




&
-
breaks down worn-out cells or



digests food
*

simple organisms

, Extracellular Enzymes
·


organelles are
specialised parts of a cell that
carry out a




paticular function
membrane bound
some
organelles are
-




involved and include
organelles in the
production secretion
of proteins :


> Nucleus


Transcription of DNA
-




> Ribosomes

Translation to
produce proteins
-




Endoplasmic transports proteins
+
>
Rough Reticulum Synthesises
-




>
Golgi Apparatus prepares (packages) protein for transport
-




Cell Membrane
>
Surface
-
vesicle
containing protein fuses with the
surface membrane for secretion




(RER)
Rough Endoplasmic Reticulum
secreted become
proteins produced can
The be out the cell
of or



attached to the cell
surface membrane inside
space of
↓ the RER
Proteins are
folded and
processed in the lumen

Ribosomes that the
in the
cytoplasm synthesise proteins stay within
-




Cell




Golgi Apparatus
Processed RER
transported to the
proteins from the are
Golgi apparatus
-




in Vesicles


They fuse with the Golgi apparatus
-




This releases the the Golgi
proteins into
-




The Golgi apparatus modifies the them
proteins preparing for secretion
-




,



Proteins that in the
Golgi apparatus are
usually
-




go
:



>
Exported
Put into
lysosomes
Delivered to membrane-bound
>
organelles

The
large called
·

movement of a molecule out
of
a cell
using a vesicle is



exocytosis